Biased pivoting cartridge extractor for blowback bolt firearms

ABSTRACT

A biased pivoting spent ammunition cartridge case extractor and retainer mechanism for blowback bolt firearms. The mechanism includes a distal arcuate hook shaped and dimensioned to intimately engage and nest into part of the circumferential groove in front of the cartridge rim. The hook remains engaged during blowback extraction of the casing from the chamber, and prior to ejection of the case from the firearm. The hook is formed onto the distal end of a rocking member secured to the bolt by a medial pivot. A compression spring bears against the opposite, proximal end of the rocking member thereby biasing the hook inwardly toward the counterbore seat on the distal end of the bolt into which the base of the case rests during extraction. A direct gas impingement system overcomes the biasing force of the spring to cause the case to be ejected.

PRIOR APPLICATION

This application is a continuation of U.S. patent application Ser. No. 16/264,132, filed 2019 Jan. 31, which is a continuation of U.S. patent application Ser. No. 15/711,822, filed 2017 Sep. 21 which claims the benefit of U.S. Provisional Patent Application Ser. No. 62/397,817, filed 2016 Sep. 21, and U.S. Provisional Patent Application Ser. No. 62/397,812, filed 2016 Sep. 21, both of which are fully incorporated herein by reference.

FIELD OF THE INVENTION

The invention relates to firearms, and more particularly to automatic spent cartridge extraction mechanisms for blowback style firearms.

BACKGROUND

Most firearms provide mechanisms to facilitate the automated handling of ammunition and their waste products. A firing cycle can include the stages of: stripping an unfired ammunition cartridge from a spring-loaded multi-cartridge magazine; chambering the cartridge; firing; extraction of the spent cartridge casing from the chamber; and, ejection of spent cartridge casing from the firearm. A blowback bolt mechanism uses some of the force of the pressurized gasses generated by the burning propellant in the cartridge to accomplish operation of the cycle in an automatic or semiautomatic way.

It can be appreciated that spent cartridge casing extractors have been used with blowback style bolt action firearms for many years. Typically, prior blowback style extractors have used a beam, or flexure-type, leaf spring extraction mechanism.

An important problem with such mechanisms is that minor variations in beam thickness due to manufacturing imprecision can cause deviations in beam strength, thus changing the resiliency of the beam and the forces it applies. It is understood that the strength of a beam changes by the cube of its deviation in thickness. Therefore, even very slight changes in thickness can adversely affect cartridge manipulation by the extractor mechanism during loading into the firing chamber, and during cartridge casing ejection after firing due to deviation in energy absorption or transmission.

Similarly, minor variations in the material characteristics of these mechanical parts can adversely affect performance. Characteristics such as material strength, coefficient of friction because of coating or surface irregularities, and other material properties can similarly adversely affect the resiliency properties of the beam.

Another problem with conventional blowback bolt extractors using the beam bending design is that there is a narrow optimum range of deflection required to properly interface with the cartridge casing during extraction and eventual ejection. It is often difficult to achieve such a narrow optimum range of operation due to vagaries in manufacturing and/or assembly.

While conventional extractor designs may be suitable for precisely manufactured, carefully assembled, and well-maintained firearms using precisely manufactured ammunition cartridges, they may not be suitable for firearms that must easily operate over a wide range of cartridge and bolt tolerances, while still providing low force absorption during loading, and positive and consistent retention during cartridge casing ejection.

Rifles such as the AR-15 and M-16 firearms utilize a Direct Gas Impingement (DGI) type of blowback extractor wherein the flow of residual firing gases provide the necessary force to extract the spent cartridge casing from the chamber and eject it off of the bolt counterbore at the appropriate time. Such designs are impractical in the narrow confines of handgun type firearms.

Therefore, there is a need for an automatic spent cartridge casing extraction mechanism which better accommodates minor manufacturing variation in cartridges and firearm parts, which better accommodates wear, and which better maintains alignment of the cartridge and bolt during chambering and extraction. There is a need for a cartridge extractor mechanism which operates over a wide range of cartridge and bolt tolerances, which provides low force absorption during loading, and which provides positive and consistent retention of the cartridge prior to ejection from the firearm.

In other words, there is a need for an automatic spent cartridge extraction mechanism which addresses some or all of the above identified inadequacies.

SUMMARY

The principal and secondary objects of the invention are to provide an improved cartridge extractor mechanism for blowback bolt firearms. These and other objects are achieved by a biased pivoting cartridge extractor mechanism mounted to the bolt of the firearm.

In some embodiments there is provided a biased pivoting cartridge extractor that will operate over a wider range of cartridge and bolt tolerances with low force absorption during loading, and positive and consistent retention of the cartridge during ejection from the firearm.

In some embodiments there is provided a biased pivoting cartridge extractor pivotingly secured to an axially slidable bolt. In some embodiments the extractor has a cartridge contacting feature that is biased radially inwardly toward the cartridge seat location on the bolt by a compression spring located on the opposite end from the pivot. In some embodiments a compression spring loads the extractor against the cartridge rim, and thus the cartridge rim against the cartridge counterbore within the bolt.

In some embodiments there is provided a blow-back style of firearm bolt modified to accept a Direct Gas Impingement style of cartridge extractor.

In some embodiments there is provided an extractor based in part on the style of an AR-15 or M-16 type of extractor to retain relative alignment of the cartridge to the cartridge counterbore in the bolt during cartridge ejection.

In some embodiments there is provided a cartridge extractor that properly engages a cartridge through a wide range of dimensional tolerances for the bolt, extractor, and cartridge.

In some embodiments there is provided a cartridge extractor that is not greatly impacted by material strength inconsistencies.

In some embodiments there is provided a cartridge extractor that is not greatly impacted by deviations in the surface coefficient of friction.

In some embodiments there is provided a cartridge extractor that has greater resistance to cyclic fatigue.

In some embodiments it is provided that in a firearm having a bolt reciprocatingly sliding axially along a bolt axis, said bolt temporarily engaging an ammunition cartridge at a distal bolt seat during a firing cycle, wherein said ammunition cartridge includes a case portion having a proximal rim adjacent to a circumferential groove, an improvement which comprises: an extractor assembly which comprise: an oblong rocking member comprising a hook radially moveable with respect to said bolt; and, said oblong rocking member being pivotingly secured to said bolt at a pivot.

In some embodiments said hook is biased radially inwardly by a biasing force.

In some embodiments said biasing force is overcomeable by an ejector selected from the group consisting of a mechanical ejector, and direct gas impingement of pressurized gaseous forces generated during said firing cycle.

In some embodiments said pressurized gaseous forces comprise a radial component impacting said case portion during an ejection stage of said firing cycle.

In some embodiments the improvement further comprises a spring between said bolt and said rocking member, said spring providing said biasing force.

In some embodiments said rocking member comprises: a distal end portion carrying said hook; a proximal end portion; and, a medial portion secured to said pivot.

In some embodiments said spring comprises a first terminus bearing against said bolt and a second terminus bearing against said proximal end portion of said extractor member.

In some embodiments said pivot comprises a pivot pin defining an extractor axis of rotation; said pivot pin having a substantially cylindrical post rotatively engaging a substantially cylindrical bearing.

In some embodiments said extractor axis of rotation is perpendicular to said bolt axis.

In some embodiments said rocking member moves within a recess formed into said bolt.

In some embodiments said rocking member rocks within a plane angularly inclined between about 66.5 degrees and about 68.5 degrees from vertical with respect to the firearm in a upright orientation.

In some embodiments said hook comprises a concave arcuate tip shaped and dimensioned to intimately nest against a convex surface of said circumferential groove; and, wherein said concave arcuate tip is further dimensioned to have an axial dimension less than the axial dimension of said circumferential groove.

In some embodiments said arcuate tip and curved outer surface of said cartridge have commensurate radii of curvature.

In some embodiments said hook further comprises a pair of convex corners at the angular extremities of said arcuate tip.

In some embodiments said bolt has a distal face having a counterbore seat and an axially proximally recessed lip adjacent to said seat on a lower portion of said distal face.

In some embodiments it is provided that in a method for securing a spent ammunition cartridge case against a seat of a bolt during a firing cycle prior to ejection of said case from a firearm, said cartridge case having a proximal rim adjacent to a circumferential groove, an improvement which comprises: contacting a proximal rim of said case against said seat; and, simultaneously to said contacting, engaging said circumferential groove of said case by a hook of an extractor member pivotingly mounted to said bolt.

In some embodiments the improvement further comprises radially biasing said hook against said case.

In some embodiments said radially biasing occurs with a force overcomeable by direct gas impingement forces generated by during said firing cycle.

The text of the original claims is incorporated herein by reference as describing features in some embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagrammatic cross-sectional and partially enlarged side view of a firearm having a blowback bolt having a pivoting cartridge extractor according to an exemplary embodiment of the invention.

FIG. 2 is a diagrammatic perspective view thereof.

FIG. 3 is a diagrammatic, enlarged cross-sectional side view thereof.

FIG. 4 is a diagrammatic end view showing the angular location of the extractor on the bolt.

FIG. 5 is a diagrammatic, cross-sectional side view thereof during cartridge firing and extraction.

FIG. 6 is a diagrammatic, cross-sectional side view thereof during cartridge ejection.

FIG. 7 is a diagrammatic, perspective view of a blowback bolt having a pivoting cartridge extractor according to an alternate exemplary embodiment of the invention.

FIG. 8 is a cross-sectional view of the blowback bolt of FIG. 7 taken perpendicular to the pivot axis of the extractor.

FIG. 9 is a cross-sectional side view of the blowback bolt of FIG. 7 as a cartridge is being chambered.

FIG. 10 is a cross-sectional front view of the blowback bolt of FIG. 7 showing the cartridge rim cartridge becoming seated in the counterbore seat.

FIG. 11 is a cross-sectional side view of the blowback bolt of FIG. 7 showing the cartridge being stripped from the magazine for chambering.

FIG. 12 is a cross-sectional side view of the blowback bolt of FIG. 7 showing the cartridge fully chambered.

FIG. 13 is a cross-sectional side view of the blowback bolt of FIG. 7 showing the spent cartridge casing being ejected by a mechanical ejector.

DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

It is important to note that in the exemplary embodiments shown, many critical firearm features, such as the firing pin, triggering mechanisms, ejector mechanisms, and direct gas impingement channeling have been omitted from some of the firearm illustrations in order to improve clarity. Those skilled in the art will readily recognize where such features can be expected to reside in a more complete illustration.

Further, the viewpoint of the cross-section in FIGS. 1, 5, and 6 is taken generally from a the side of the firearm. However, to properly indicate the operation of the various features, their angular locations with respect to the bolt axis have been adjusted to fall within the vertical plane. Those skilled in the art will readily appreciate that such features can be located in angularly different locations in an operational firearm.

Referring now to the drawing, there is illustrated in FIGS. 1 and 2, a semiautomatic pistol type firearm 11 similar to a Glock brand 9 mm pistol commercially available from the Glock, Inc. company of Smyrna, Ga. The firearm includes an elongated barrel 12 extending between a distal muzzle (not shown) and a proximal chamber 13 for holding an ammunition cartridge 15 during firing. Additional cartridges 14 are successively loaded from a magazine 16 into the chamber by operation a bolt 20 which reciprocatingly slides 21 along an axis 9 substantially parallel to the barrel. The distal end of the bolt can have a counterbore forming a seat 23 for nesting the proximal base or rim 17 of the cartridge casing 18 during the firing and extraction stages of the firing cycle. The bolt also carries a firing pin (not shown) which axially strikes the primer set into the cartridge base to initiate the firing of the cartridge.

Except where otherwise noted, the terms “axial”, “axially”, “radial”, and “radially” are in reference to the bolt 20 sliding axis 9. Further, “front”, “forward” and “forwardly” can be used to denote the distal part of a structure or the distal direction toward the muzzle, and “rear”, “rearward” and “rearwardly” can be used to denote the proximal part of a structure or the proximal direction opposite from the distal direction.

An extractor assembly 30 is secured to the bolt 20 near its distal end 24. The extractor assembly includes an oblong, rigid rocking member 31 pivotably secured to the bolt by a pivot 40 allowing rotation 42 of the member about a pivot axis 41 substantially perpendicular to the sliding axis 9 of the bolt. Thus the rocking member has a reciprocating direction of movement which lies within a plane that can include the bolt axis. The pivot can be formed by a pivot pin defining the pivot axis of rotation. The pivot pin can be a substantially cylindrical post rotatively engaging a substantially cylindrical bearing.

The rocking member 31 can have a pair of arms 33,34 straddling the pivot. A first, distal arm 33 extends substantially axially distally terminating in a hook structure 35 at its distal end. A second, proximal arm 34 extends substantially axially proximally terminating in a proximal end 36. In this way, when the rocking member proximal end moves radially outward, the distal, hook end moves radially inward with respect to the bolt sliding axis 9. A compression spring 60 captured within a pair of opposed wells 38,39 formed into corresponding surfaces of the bolt and proximal arm of the extractor member biases the proximal end of the member radially outward so that the hook structure is correspondingly biased radially inward. The spring has a first terminus 61 which bears against the bolt and a second terminus 62 which bears against the proximal arm of the extractor member.

The extractor member 31 can reside substantially within a commensurately shaped recess 50 formed into a radially outward portion of the bolt 20 so that a radially outward surface 44 of the extractor member can be substantially flush with the radially outward surface 45 of the bolt in order to further reduce wear and the potential for jamming. Further, the distal face 47 of the extractor member is substantially coplanar with the upper distal face 48 forming the strike surface of the bolt bordering the counterbore 23 which is furthest from the magazine 16.

The extractor member 31 can have a medial support 51 for carrying the pivot 40 at a position radially inward from the proximal arm 34 and the distal arm 33 so that the center of rotation is closer to the centerline of the bolt 20 which can enhance the distribution of loads on the extractor mechanism. The shape and dimensioning of the recess 50 is selected to create a gap 52 between the member arms and the bolt, allowing the limited rocking movement of the member in order to help accommodate the variability in cartridge and firearm parts described above. The compression spring 60 applies, through the pivot 40 a radially inward biasing force F against the cartridge casing 18 to bias the rim 17 against the wall structures 19,58 at the periphery of the counterbore seat 23.

The hook 35 is shaped, dimensioned and positioned axially to engage and bear against the circumferential groove 22 axially separating the proximal rim 17 of the cartridge 15 from the rest of the casing 18. Thus the hook will have an axial dimension less than the axial dimension of the circumferential groove. The hook can have a concave arcuate tip 54 shaped and dimensioned to intimately nest against a convex surface of said circumferential groove. Thus the arcuate tip and circumferential groove can have commensurate radii of curvature. The hook can also include a pair of rounded, convex corners 55,56 at the angular extremities of the arcuate tip to reduce the potential for jamming. In this way the biased hook of the extractor mechanism can both axially and radially load the casing against the counterbore relief structures in order to captivate or retain the rim of the casing during extraction and until ejection. The dimensioning of the extractor is selected so that the hook at the engagement end of the extractor rests at a location smaller in diameter than when a cartridge is seated on the bolt counterbore. In other words the there is a snap-fitting type arrangement between the rim of the cartridge and the counterbore seat.

As shown in FIG. 3, the distal face 48 forming the impact surface of the bolt 20 is located an axial distance distally D1 from the lower lip 49 closest to the magazine, which itself is located and axial distance D2 from the counterbore seat 23. The lower lip is supported by a distally projecting pedestal 57 radially adjacent to a lower edge of the counterbore seat 23. The distal face of the bolt, the lower lip, and the counterbore seat can all reside substantially within planes P1,P2,P3 parallel to one another and perpendicular to the sliding axis 9 of the bolt. This axially relieved lip on the lower edge of the distal end of the bolt, and the corresponding wall structures on the periphery of the counterbore seat, help provide greater control over the cartridge 15 as it is being stripped from the magazine and chambered. The lip includes a concave arcuate wall 58 facing radially inwardly which is shaped and dimensioned to nest against a convex surface of the cartridge rim 17.

The axially relieved lip and counterbore form an arcuate, partial, distally projecting, upper guidewall 19 on the upper portion of the bolt distal end. The guidewall and cartridge rim edge can have commensurate radii of curvature. The guidewall can extend in an angularly limited manner around the upper periphery of the counterbore seat terminating in a pair of lateral guides 61,62 at the angular extremities of the guidewall, and leaving an angular gap around the lower periphery of the seat. The lip, guides, and hook serve to guide the rim of the cartridge into the seat in a smooth scooping or funneling manner as the cartridge is stripped from the magazine and chambered.

As stated above and as shown in FIG. 4, the location of the extraction mechanism 30 can be attached to the bolt 20 at a location where the plane of the rocking motion Pr forms a non-zero angle A with the vertical plane Pv of the firearm. For many handgun style firearms where space is limited, the angle of the rocking plane from vertical with respect to the firearm in a upright orientation can preferably be between about 65 degrees and about 70 degrees, more preferably be between about 66.5 degrees and about 68.5 degrees, and most preferably about 67.5 degrees.

Referring now to FIG. 5, during firing, rapidly expanding gasses 70 propel the projectile portion 71 of the cartridge distally along the barrel 12 and out the muzzle. This same gasses can propel the spent cartridge casing 18 in the proximal direction to extract it from the chamber 13 and push the bolt 20 rearwardly. Since the base of the casing is bearing against the seat of the bolt, both the casing and bolt are driven proximally. It shall be understood that the relative locations of the projectile and bolt are shown for illustrative purposes and may not accurately reflect their actual positions at any given time. The hook 35 of the extractor rocking member 31 remains engaged into the circumferential groove at the rear end of the casing to securely hold it against the counterbore seat 23 of the bolt during blowback extraction of the casing from the chamber, and prior to ejection of the case from the firearm.

In FIG. 6, the expanding gasses 70 and the momentum of the bolt 20 move the bolt further in the proximal direction along the bolt sliding axis 9 so that the casing 18 has an axial position in line with a radial exit port 75. An ejector causes the casing to dislodge from the counterbore seat 23 and be ejected from the firearm. The ejector can be a mechanical ejector as shown in FIG. 13 in connection with an alternate embodiment, or through Direct Gas Impingement (DGI) which provides a radial component to the expanding gas forces which dislodge and ejects the casing. At this time the force of the compression spring 60 has been overcome, allowing the rocking member 31 to rotate such that the hook 35 moves radially outwardly.

In this way the above described embodiments achieve a cartridge extractor which operates over a wide range of cartridge and bolt tolerances, has low force absorption during loading, and achieves positive and consistent retention of the cartridge during ejection from the firearm.

Referring now to FIGS. 7-13 there is shown an alternate exemplary embodiment of the invention. The interconnections of the main components of this invention are the extractor (FIG. 7, 110), the pivot pin (FIG. 8, 220), the compression spring (FIG. 8, 230), and the bolt (FIG. 7, 140). This blow-back bolt extractor is a stark departure from prior art beam flexure designs currently employed by all firearms manufacturers in the market. This novel application utilizes a compression spring (FIG. 8, 230) at the opposite end from the cartridge (FIG. 8 250), with a pivot in the middle (FIG. 8, 220) offering a wider range of radial operation with a flatter rate for spring force encountered. This lower rate of spring force encountered by the cartridge (FIG. 9, 350) while loading offers the ability to physically load the extractor (FIG. 10, 410) axially against the cartridge (FIG. 10, 450) to restrain the opposite side of the cartridge rim against the counter bored cartridge seat (FIG. 10, 465) within the bolt (FIG. 10, 440).

This extra cartridge restraint maintains a more consistent control over the cartridge during the blow-back stage of the firing cycle of the firearm immediately after firing until the ejector (FIG. 13, 770) engages the cartridge (FIG. 13, 750) to eject the cartridge from the firearm to ready for the next loading and firing cycle. Alternately, instead of a compression spring biasing the proximal extractor arm away from the bolt, an extension spring can bias the distal extractor arm out toward the bolt. In other words, instead of the described compression spring pushing out from bolt centerline under the extractor at the opposite end of the cartridge end of the extractor, an extension spring pulling the cartridge end of the extractor in toward the bolt centerline can be used. Alternate variations would be of any pivoting extractor non-beam or leaf spring extractor pocketed into a blow-back bolt.

Upon the bolt being released from the ready position (FIG. 11, 540), the bolt moves toward the barrel (FIG. 11, 560) and strips a cartridge (FIG. 11, 550) from the magazine (FIG. 11, 552) and moves it toward the barrel chamber (FIG. 11, 562). At first contact between the bolt (FIG. 11, 540) and the cartridge (FIG. 11, 550), the extractor (FIG. 11, 510) is not actuated. Roughly one-halfway through the cartridge chambering cycle the cartridge (FIG. 10, 450) rises vertically sufficiently to contact the extractor (FIG. 10, 410). In the strip-lip (FIG. 9, 312) style of bolt shown, this actuation of the extractor (FIG. 9, 310) is accomplished by the radial movement of the cartridge (FIG. 9, 350) as it is scooped up toward the bolt centerline as the bolt moves the cartridge (FIG. 9, 350) to final seating within the barrel chamber (FIG. 9, 362). As the bolt (FIG. 12, 640) moves the cartridge (FIG. 12, 650) into the fully chambered position (FIG. 12, 652), the cartridge rim is physically biased, or loaded against the opposite wall of the bolt recess for the cartridge (FIG. 10, 465).

Upon firing of the cartridge round, part of the expelled energy from the fired cartridge is utilized in moving the firearm bolt rearward for cartridge casing ejection, and positioning of the bolt for re-chambering another cartridge round. This force is transferred through the rearward movement of the cartridge, then to the forceful rearward movement of the bolt by the cartridge blow-back. The extractor maintains control of the rear of the cartridge at the rim while the kinetic energy of the fired cartridge round moves the cartridge, bolt, extractor, pivot and spring rearward. At a specified position in the ejection stage of the firing cycle, the control of the cartridge by the extractor and bolt is overcome by an additional force of an ejector that strips the cartridge casing from the bolt and extractor retention in order to expel it from the firearm. For direct gas impingement firearms, pressurized firing gasses can be channeled to provide radial forces necessary to accomplish ejection. For bolts without the strip-lip type of dual plane (FIG. 9, 312) cartridge contact face, extractor engagement is later in the loading cycle with an axial engagement to the extractor as the cartridge moves axially into the counter bored cartridge retaining position.

In this way the extractor helps retain relative alignment of the cartridge case to the cartridge counterbore seat on the distal end of the bolt during extraction and prior to cartridge ejection.

FIGS. 7-13 illustrate a cartridge extractor, which comprises the bolt, extractor, and compression spring implemented on a blow-back style of firearm bolt modified to accept a direct gas impingement style of operation. The extractor is based in part on the style of an AR-15 or M-16 type of extractor to retain relative alignment of the cartridge to the cartridge counterbore in the bolt during cartridge ejection. A compression spring loads the extractor against cartridge, and cartridge against the cartridge counterbore within the bolt. A blow-back style of firearm bolt is thus modified to accept a Direct Gas Impingement style of cartridge extractor. The bolt in general looks and functions much like any other blow-back bolt such as a Glock or Colt with the exception that the extractor is not of a leaf spring type of design as used in prior art designs. The present exemplary embodiment has modifications within to allow the utilization of Direct Gas Impingement (DGI) style of the DGI bolt carrier group extractor such as that used by the AR-15 or M-16 firearms. The bolt is deviating from the high force bent beam extractor of the traditional blow-back bolts. The present exemplary embodiment bolt is machined for a pivot pin and pocketed for clearance for an AR style of extractor.

The present exemplary embodiment provides an extractor based in part on the style of an AR-15 or M-16 type of extractor to retain relative alignment of the cartridge to the cartridge counterbore in the bolt during cartridge ejection. The extractor is of a design created for the totally different operating Direct Gas Impingement (DGI) system. In prior art utilization this extractor operates within the bolt carrier group wherein this extractor is captivated between the bolt and bolt carrier, and limited in outward movement by the bolt carrier.

The DGI version imparts axial loading to the cartridge only for extraction. In the present exemplary embodiment the blow-back bolt extractor operates within the modified bolt only, and imparts radial loading of the cartridge against the counterbore relief of the bolt as well as axial loading for overall retention and control during cartridge ejection, and is unrestrained at ejection when the bolt is telescopically unrestrained by the first rearward movement of the bolt carrier.

The present exemplary embodiment utilizes this pivoting extractor design that is preloaded against the cartridge with a compression spring to offer a greater operational travel with a flatter force deviation than the prior art blow-back bolts utilizing a bending beam, thus deviating from the high force bent beam extractors of traditional blow-back bolts. The present exemplary embodiment provides an extractor having a low force pivoting design biased into the retention position by a compression spring offering less interference force to the cartridge, and less flexural fatigue to the spring.

In the present exemplary embodiment the compression spring loads the extractor against cartridge rim. The spring can be a conventional compression spring on the opposite end of the pivot that loads the engagement end of the extractor against the cartridge at the extraction rim. Alternately, the spring force can be accomplished by an extension spring on the other side.

As to a further discussion of the manner of usage and operation of the present invention, the same should be apparent from the above description. Accordingly, no further discussion relating to the manner of usage and operation will be provided. With respect to the above description then, it is to be realized that the optimum dimensional relationships for the parts of the invention, to include variations in size, materials, shape, form, function and manner of operation, assembly and use, are deemed readily apparent and obvious to one skilled in the art, and all equivalent relationships to those illustrated in the drawings and described in the specification are intended to be encompassed by the present invention. Therefore, the foregoing is considered as illustrative only of the principles of the invention. Further, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation shown and described, and accordingly, all suitable modifications and equivalents may be resorted to, falling within the scope of the invention.

Although the above embodiment or embodiments of the invention have been described in detail, it is to be understood that the invention is not limited in its application to the details of construction and to the arrangements of the components set forth in the description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced and carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein are for the purpose of the description and should not be regarded as limiting.

While the exemplary embodiments of the invention have been described, modifications can be made and other embodiments may be devised without departing from the spirit of the invention and the scope of the appended claims. 

What is claimed is:
 1. In a firearm having a bolt reciprocatingly sliding axially along a bolt axis, said bolt temporarily engaging an ammunition cartridge at a distal bolt seat during a firing cycle, wherein said ammunition cartridge includes a case portion having a proximal rim adjacent to a circumferential groove, an improvement which comprises: an extractor assembly which comprise: an oblong rocking member comprising a hook radially moveable with respect to said bolt; and, said oblong rocking member being pivotingly secured to said bolt at a pivot.
 2. The improvement of claim 1, wherein said hook is biased radially inwardly by a biasing force.
 3. The improvement of claim 2, wherein said biasing force is overcomeable by an ejector selected from the group consisting of a mechanical ejector, and direct gas impingement of pressurized gaseous forces generated during said firing cycle.
 4. The improvement of claim 3, wherein said pressurized gaseous forces comprise a radial component impacting said case portion during an ejection stage of said firing cycle.
 5. The improvement of claim 2, which further comprises a spring between said bolt and said rocking member, said spring providing said biasing force.
 6. The improvement of claim 5, wherein said rocking member comprises: a distal end portion carrying said hook; a proximal end portion; and, a medial portion secured to said pivot.
 7. The improvement of claim 6, wherein said spring comprises a first terminus bearing against said bolt and a second terminus bearing against said proximal end portion of said extractor member.
 8. The improvement of claim 7, wherein said pivot comprises a pivot pin defining an extractor axis of rotation; said pivot pin having a substantially cylindrical post rotatively engaging a substantially cylindrical bearing.
 9. The improvement of claim 8, wherein said extractor axis of rotation is perpendicular to said bolt axis.
 10. The improvement of claim 1, wherein said rocking member moves within a recess formed into said bolt.
 11. The improvement of claim 1, wherein said rocking member rocks within a plane angularly inclined between about 66.5 degrees and about 68.5 degrees from vertical with respect to the firearm in a upright orientation.
 12. The improvement of claim 1, wherein said hook comprises a concave arcuate tip shaped and dimensioned to intimately nest against a convex surface of said circumferential groove; and, wherein said concave arcuate tip is further dimensioned to have an axial dimension less than the axial dimension of said circumferential groove.
 13. The improvement of claim 12, wherein said arcuate tip and curved outer surface of said cartridge have commensurate radii of curvature.
 14. The improvement of claim 13, wherein said hook further comprises a pair of convex corners at the angular extremities of said arcuate tip.
 15. In a method for securing a spent ammunition cartridge case against a seat of a bolt during a firing cycle prior to ejection of said case from a firearm, said cartridge case having a proximal rim adjacent to a circumferential groove, an improvement which comprises: contacting a proximal rim of said case against said seat; and, simultaneously to said contacting, engaging said circumferential groove of said case by a hook of an extractor member pivotingly mounted to said bolt.
 16. The improvement of claim 15, which further comprises radially biasing said hook against said case.
 17. The improvement of claim 16, wherein said radially biasing occurs with a force overcomeable by direct gas impingement forces generated by during said firing cycle. 